docs: def save_credentials(self, profile="default"):
          """
          Save your database credentials so you don't have to save them in script.
  
          Parameters
          ----------
          profile: str
              (optional) identifier/name for your database (i.e. "dw", "prod")
  
          from db import DB
          import pymysql
          db = DB(username="hank", password="foo", hostname="prod.mardukas.com", dbname="bar", dbtype="mysql")
          db.save_credentials(profile="production")
          db = DB(username="hank", password="foo", hostname="staging.mardukas.com", dbname="bar", dbtype="mysql")
          db.save_credentials(profile="staging")
          db = DB(profile="staging")
  
          >>> from db import DemoDB
          >>> db = DemoDB()
          >>> db.save_credentials(profile='test')
          """
          f = profile_path(DBPY_PROFILE_ID, profile)
          dump_to_json(f, self.credentials)